A wide variety of medical catheterization procedures involve the cooperative use of a guidewire over which the catheter can be threaded so that the guidewire can guide the catheter to the intended site in the patient's body. The use of a guidewire reduces the risk of trauma to the patient by the advancing catheter and enables the catheter to be advanced quickly, thereby reducing the time required for the procedure. The guidewire typically is more easily manipulated by the physician into a desired position in the patient's body than is the far more flexible catheter. After the guidewire has been directed to the desired location in the body, the catheter then can be threaded over and along the guidewire, with the wire providing support and guidance for the flexible catheter.
Guidewires are used frequently in connection with catheters adapted for the diagnosis or treatment of the cardiovascular system. They are useful particularly in connection with those procedures where it may be necessary for the physician to use a series of different catheters that are inserted into and withdrawn from the patient. Each of the catheters may be provided with a different shape, size, configuration or implement suited for a specific purpose. For example, angiographic studies typically include the use of at least three cardiac catheters including a right coronary artery catheter, a left coronary artery catheter and a pigtail catheter. Each has a different shape and configuration at its distal end (the end inserted into the patient; the opposite end, is the "proximal" end), each being designed to facilitate placement of the distal end of the catheter at specific locations within the region of the heart. By way of further example, other types of catheters may include balloon dilatation catheters intended to be placed within an obstructed (stenosed) portion of an artery and then inflated under high pressure to expand the lumen of the artery and improve blood flow through the artery. Such a dilatation procedure is commonly referred to as "angioplasty" and has had significantly increased use for nearly two decades in the treatment of coronary artery disease. Still other types of catheters, such as atherectomy catheters, catheters incorporating optical elements for the transmission of light, catheters used in the delivery of a stent, among others, often are used in connection with guidewires.
It is common in the use of wire guided catheters for the physician to withdraw the catheter from the patient and substitute another catheter in its place. When doing so, it is desirable to leave the guidewire in place in order that the guidewire can be used to advance the succeeding catheter directly to the treatment site with a minimum of delay and trauma. In order to maintain the guidewire in place while withdrawing the catheter, the guidewire must be held in its position in the blood vessel as the catheter is withdrawn. The catheter, however, typically is longer than the proximal portion of the guidewire that protrudes out of the patient. Thus, before the catheter is fully withdrawn it completely covers the proximally extending end of the guidewire such that the physician can no longer grasp the guidewire. In order to effectively remove the catheter while permitting the guidewire to remain in place, some means must be provided to prevent the guidewire from being dragged out of position as the catheter is removed. This problem is frequently encountered in coronary angioplasty procedures and, therefore, the present invention, and its background, will be described in the context of a percutaneous trans luminal coronary angioplasty (PTCA) system.
Dilatation catheters commonly used in PTCA include an elongate flexible shaft of the order of about 150 cm long having a dilatation balloon mounted to the distal end of the shaft and an inflation lumen extending longitudinally within the shaft from the proximal end to the interior of the balloon so that the balloon may be inflated and deflated. Often such PTCA catheters also are provided with a full length guidewire lumen that receives a guidewire and terminates in openings at the distal tip of the shaft and at the proximal end of the catheter. When the guidewire and catheter are placed within a patient's artery, the guidewire can be manipulated and navigated to a desired location. The catheter then can be advanced, guided by the guidewire, to that location.
Typically, the balloon dilatation catheter and guidewire are guided to the entrance of one of the coronary arteries through another previously placed, larger diameter, single lumen catheter (a guide catheter). The guide catheter commonly is percutaneously inserted into the patient's femoral artery and is advanced along the aorta toward the heart. The guide catheter typically is provided with a pre-shaped distal tip adapted to engage and remain at the coronary ostium leading to the coronary artery. Once positioned, the guide catheter remains in place throughout the procedure to provide direct, quick access to the entrance of the coronary artery.
It is common during a PTCA procedure for the physician to exchange the balloon catheter for another catheter. This may occur if the physician initially performed a partial dilatation with a small diameter balloon and then wished to further dilate the patient's artery by using a catheter having a larger balloon. Catheters may also be exchanged to perform further operations in the artery such as stent placement or other treatment. Several techniques are commonly used to exchange a catheter, all designed to enable withdrawal of the catheter without losing guidewire position.
Among the techniques for effecting a catheter exchange is one in which the conventional guidewire (approximately 175-190 cm long) is removed from the indwelling balloon catheter and is replaced with a longer exchange wire, usually about 300 cm long. The additional length of the exchange wire results in a long proximally protruding portion that is longer than the catheter to be withdrawn. When the balloon catheter is withdrawn, some part of the proximally extending portion of the exchange wire will always be exposed to provide a means by which the exchange wire can be grasped and its position in the blood vessel maintained. After the 300 cm exchange wire has replaced the conventional length guidewire, the original catheter then is withdrawn over the exchange wire, which is grasped and held in place by an assistant. The next succeeding catheter then can be inserted into the patient over the exchange wire. The exchange wire provides a direct path to guide the new catheter to the portion of the blood vessel to be treated. If desired, the exchange wire then may be removed and replaced with a conventional length guidewire, although some physicians may prefer to permit the exchange wire to remain in place for the remainder of the procedure, especially if additional catheter exchanges are contemplated.
The technique of using a long exchange wire is not free from difficulty. The proximally extending end of the exchange wire is quite long and cannot be manipulated easily, should it be desired to do so. Typically, the use of a long exchange wire requires removal of the original standard length guidewire and replacement with the exchange wire. An assistant must hold the proximal end of the exchange wire at all times so that it does not fall to the floor, become kinked or contaminated. The placement of the exchange wire is performed under fluoroscopy to assure that it is properly placed in the patient's blood vessel. The use of a separate exchange wire also adds to the time and complexity of the procedure.
Another technique omits the necessity for an exchange wire by providing a guidewire extension that is attached to the proximal end of the conventional length indwelling guidewire, thereby effectively extending the length of the portion of the guidewire that protrudes out of the patient. The guidewire length is extended sufficiently to permit the catheter to be withdrawn and a new catheter to be threaded back into the patient without losing guidewire position. U.S. Pat. No. 4,917,103 discloses an illustrative guidewire extension system.
It would be desirable to provide a simple, effective and inexpensive system and technique for providing an extended length guidewire to enable withdrawal of an indwelling over-the-wire catheter while leaving the guidewire in place and to provide a system to facilitate catheter exchanges. It is the general object of the present invention to provide such a system.